Nature of Algae Problems

in MarylandAlgal growth during the springand summer in ponds, lakes, andmunicipal reservoirs can pose anumber of prob lems. Algae growingin ponds that are used for irrigationcan clog pumps, block fi lters, andca use odor problems; uncontrolledgrowth is also very unsightly. Algalblooms seem to be more severe inbodies of water with high levels ofnutrients, particu larly nitrogen andphosphorus - such high co ncenlevels are present in the water, alga ltrations are often the resul t of run offblooms w ill still have to befrom agri cul tura l or waterfow lco ntrolled.activity, suburban development orTh e use of barl ey straw to co ntrolindustria l sites.alga l growth in freshwater systems isDi fferent species of algae blooma fai rly new deve lopment. Th e disyea r-round in ponds, lakes andcovery itse lf w as accidenta l. Accordreservo irs and are a major source ofing to on e account, a bale of barl eyconce rn for managers. Watershedstraw dropped from a Briti sh fa rmer'smanagement practi ces ca n have along term impact on run off into these w agon, fell into a pond th at had asevere algae probl em - the algaebodies of wa ter. For example, ifgraduall y di sappea red and did notlands cl ea red for development arereturn th at season . The farmer repornot well protected, sediment andted hi s observation s to a researchernutrient runoff ca n lead to alga l prowho was investiga ting innovativeli ferati on th at may in turn produ cetechniques for controlling pondintractabl e taste and odor probl emsalgae, an important issue in thein potabl e wa ter. Even w ith bestUnited Kingdom wh ere most bodi esmanagement practi ces in the wa terof fresh w ater are highl y eutrophicshed, forests and ripari an bu ffer stripsand chemi ca l control s are closelytake ti me to grow to a size that willregul ated.effectively protect th e lakes andreservoirs; as long as high nu tri ent

Traditional Control Options

Because bodies of water aremanaged for multiple use, consideration must be given to appropriate methods of algal control;managers must factor in the size,use, and location of the body ofwater. Best management plansfrequently use combinations ofmechanical, chemi cal, and biological techniques to optimizeeffectiveness. For examp le, controlling algae through mechanical orchemica l mea ns ca n be very costlyand/or ineffective. In addition somechemicals may limit or restrict theuse of the water for irrigation andother activities, while others canalso eliminate desirable plants. Onthe other hand, mechanical controlis only effective with filamentousforms.Colorants (dyes which absorblight necessary for algal growth) maybe an environmentally sound method of suppressing algae, but they areexpensive, and often the colors areunnatural. Chemical treatments suchas elemental copper, copper sulfate,potassium permanganate, andDiquat can also lead to problems.When applied directly to water,these materials present an evenhigher possibility for non-targetexposure than when they are used inland-based applications. Some ofthese chemicals kill vascular plants,thus allowing algae to recolonizefaster due to a lack of competitionfrom higher plants once the chemical has broken down. This situationcan then require multiple chemicalapplications to suppress the algae,thus presenting a still greater risk tonon-target organisms.Chlorination and filtration ofwater from reservoirs can take careof many species of algae, thoughSynura and Anabena spp. canpresent special problems: thesealgae release an oil that whenchlorinated causes major taste and

odor problems in the potable water

supply.

The Use of Barley Straw

Scientists have sti II not determined the chemical pathways bywhich barley straw appears tocontrol the growth of algae, thoughthe active ingredient appears to be atype of phenolic compound. Whenstraw is applied to a pond at watertemperatures below 50F, it generallytakes 6-8 weeks to become effective;at water temperatures of 68F orabove, it only takes 1-2 weeks. Onceactive, the straw may remain effective for about six months, howeverperiodic replacement appears toimprove control.It is reported that barley strawdoes not kill algae already present;rather it prevents the growth of newalgal cells. In such action it functionslike a preemergent herbicide. Theanti-algal activity is only producedwhen the straw decomposes in awell-oxygenated environment.The amount of straw needed isbased on the surface area of thepond; the volume of water seems tomake little difference. As a rule ofthumb 100-300 pounds of barleystraw (approximately 2-6 bales) peracre of surface area will providegood activity against algae. Higherrates have been shown to providebetter algal control if the problem issevere; too much straw, however,can deoxygenate the water. Oncethe water is cleared of algae, thelowest rates of application shouldprovide adequate maintenancecontrol.Barley straw is most effectivewhen loose ly app lied so that watercan move freely through it. A simp lecage works well. Empty two-literplastic bottles can serve as floats bytying them to a cage so that thebarley straw can be kept at thesurface for maximum efficiency.Multiple smaller cages are generally

better than one large one. Because

barley straw is sometimes chorpedmore finely than other types ofstraw, pieces tend to float out andsink; thus contro l is reduced. Thekey is surface area- maximizingthe exposure of the straw to thewater while retaining it in the cage.There are reports that barley strawmay be just as effective when balesare left intact, and anchored on theperimeter of the pond, so bothmethods appear to be useful.Straw should be applied in theearly spring and replenished at abouttwo-month intervals. This gives thestraw a chance to begin decomposition and get ahead of the spring/summer algal blooms that causemost of the problems for irrigationponds and other impoundments.So far there have been nonegative side effects recorded .Positive results include observationsof increased invertebrate populationsand improvement of gill development in fish from ponds wherebarley straw is applied. Barley strawshould be removed in the fall as aprecaution against oxygen depletionfrom decay of straw.

SummaryAlthough more laboratory andfield research with barley straw isnecessary to confirm the reportedeffectiveness in algae control,information availab le suggests that:

1. Barley straw does inhibit certain

types of algae, including Microcystisand Synura spp., which are waterquality management probl emsworld-wide. Barley straw is reportedto be effective against filam entous ormat-forming al gae that include anumber of different species.2. In most reported cases, barl eystraw has been benefi cial if startedea rl y in th e season and maintainedthroughout.Th ere is still some controversyover th e use of barl ey straw: it hasnot been effecti ve in ce rtain c ircumstances, for instance, in nutrient-ri chaquaculture ponds and in somegeographic areas. However, it isinexpensive, not harmful, and is infact benefi cial to other aquati corganisms . In sum, barley strawcould prove useful as part of a pondmanagement program.